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'03 G35 5AT with Spec-D catback exhaust and, Z1 HFCs, and an Injen cold air intake. H&R front coils.
very bad delayed engagement, please help transmission masters
Hey guys! '03 5AT coupe owner here.
When I come to a short stop, or even just turn around a corner, when i go to press on the gas again, instead of the transmission engaging immediately, there is a very dangerous very noticeable delay in the engagement of the transmission. This problem has gotten so bad that its started to negatively effect my daily driving and general enjoyment of the car. Thing is, my transmission definitely isn't slipping, all the gears shift fine and only first gear is a little rough. I've asked quite a few people if this is just an old trans fluid problem, and so many people advise against changing it out. I don't intend to do a full trans flush though, only a drain and fill, as to preserve the clutchpacks. I see and hear so many mixed reports about problems like this though. I don't get any check engine codes, all that happens sometimes is the revs will get a little too high before the transmission engages, and the slip light flashes and the car jerks. I know I have a dead knock sensor but I don't think this should effect the transmission at all, correct?
tldr: my transmission fluid is brown and i have delayed engagement, is there any risk in doing a drain and fill? or is my transmission cooked and i need a rebuild/swap?
Last edited by palaricky; Oct 28, 2025 at 06:47 PM.
I've heard that phrase before: "don't change your transmission fluid because there are minerals and additives that circulate and help the clutches engage".
My advice, change it immediately! I had a 07 5AT and after basic drain and fill, no more stuttering between gears and faster shifts.
In my 30+ years in getting my hands greasy and oily, i never had any issues after replacing trans oil.
I recently bought a 2015 Jaguar XFR-S with 120k texas miles that never had trans service (should be done every 60k) and the oil was brown, not clear, brown sauce!
I had to flush it once, drive it for 50 miles and flushed it again and now the trans shifts really fast, no more weird gear changes or any issues.
Do a drain and fill and see if it improves. Much cheaper than doing a trans swap right away.
You might have to reset the TCM so it goes through the relearn process. The more crap that flows through the solenoids, the faster they'll start to fail..
